A conventional light bulb is disclosed in US Publication No. 20140211475 and contain: a light-emitting module; a heat-dissipation carrier including a first surface and a second surface opposite to the first surface, disposed under the light-emitting module for conducting heat generated by the light-emitting module away from the light-emitting module; and a heat radiator disposed above the heat-dissipation carrier for radiating heat away from the heat-dissipation carrier, wherein the material of the heat-radiating material coated on the surface of the heat radiator can include carbon-containing compound such as SiC, graphene, metal oxide such as ZnO, or III-nitride compound such as BN. However, as high-power LED bulb is required to generate enough light for illumination purpose rather than direction light, the heat-dissipation design became insufficient so that the heat-dissipation carrier is often enlarged to be bulky metal heat skin, and more effective heat spreading materials are required. The developed thermal management of LED bulb increases the cost of bulbs and the cooling structure is both bulky and heavy that offsets the benefits of LED.
For light bulb application, thermal conductivity only allows heat to be conducted downward to the base. Honestly speaking, this is not efficient because filament will be connected to electronics which generate more heat. Furthermore, the power electronics will be kept in the very tight enclosure like E27/GU10 connector. The heat dissipation is problematic. Graphene has been well-known for its outstanding heat conductivity, and high surface area. Both properties indicate graphene to be a promising candidate of heat-spreading solution. However, relative designs in recent years show several shortages.
US Publication 20100085713 proposed lateral graphene as heat spreaders for electronic device and circuits. The integration process, either growing graphene by CVD process or transferring exfoliated graphene, is high cost and fairly complicated, which is not favorable for commercialization. Graphene film/papers are proposed as heat spreaders such as US publication 20130329366 and US Publication 20140224466. Graphene films were produced from graphene nanoplatelets. By compression, graphene films were formed. However, the adhesion of films onto heat source or heat sink may create another heat resistance between interfaces, and lower the heat dissipation effect.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.